Lobatocerebridae

Lobatocerebridae, which have as at end 2015 just two formally described species, are interstitial annelids without chaetae or segmentation. They are hermaphroditic deposit feeders, "microscopic, thread-like, fully ciliated animals with glandular epidermis, living interstitially between sand grains in the subtidal sandy sea-floor" (Kerbl et al 2015), and were first found off North Carolina in shallow water sediments, and monotypic until a second species, found in the Gulf of Aqaba, was formally described in 2015. "Lobatocerebromorpha" was treated as a phylum by G. Haszprunar, R. M. Rieger, and P. Schuchert (1991), and placed next to the Annelida and Sipunculida.Rouse & Fauchald (1995:274) summarised the then knowledge as follows: "Lobatocerebrum was originally described as an annelid (Rieger 1980), possibly related to the clitellates (but see Brinkhurst 1982: 1044), though they have few macroscopic 'annelid' features. Rieger (1980) reported the nephridia to be metamerically arranged, and used other cytological evidence for placing the family among the annelids. Rieger (1988: 378-379) discussed the relations among the lobatocerebrids and various groups, including annelids and acoelomate phyla, but left the position of the family undetermined. Rieger (1991) described the sperm of the lobatocerebrids as having an acrosomal tube and mitochondrial derivatives between the centrioles and the nucleus, the former present only in clitellates (Ferraguti 1983; Jamieson el al. 1987). The structures of the sperm represent potential synapomorphies for lobatocerebrids and clitellates. This implies that the absence of so many other annelid features in Lobatocerebrum are losses, or, alternatively, that they are the most plesiomorphic members of the clitellate clade. The Lobatocerebridae require further investigation."Laumer et al (2015) use the name Lobatocerebromorpha informally and found that "using 402 orthologs mined from genome and transcriptome assemblies of 90 taxa. Lobatocerebrum and Diurodrilus are found to be deeply nested members of Annelida". Kerbl et al (2015) described the anatomy of a new species, L. riegeri, the 2nd to be formally named, in great detail, using advanced techniques such as immunohistochemistry, confocal laser scanning microscopy, and TEM Weigert & Bleidorn (2016 p8) summarized phylogeny knowledge as follows: "Lobatocerebrum had originally been described as an annelid lineage (Rieger 1980, 1981). Recent investigations of the epidermis, nervous and muscular system of Lobatocerebrum riegeri using transmission electron and confocal microscopy are in line with this initial assessment (Kerbl et al. 2015). As typical for annelids, a mid-ventral nerve could be found; even though as typical for interstitial groups the overall morphology was not only similar to other interstitial annelids, but also meiofaunal members of Platyhelminthes or Gnathostomulida. However, a placement within annelids was confirmed by a phylogenomic analysis, which groups them as sister taxon of Amphinomida + Sipuncula (Laumer et al. 2015)." Martín-Durán et al. (2020: p.2) placed "Lobatocerebrum sp." (not further detailed, with molecular data apparently from Helm et al. (2018)). Dinophilus gyrociliatus and Dinophilus vorticoides together with Trilobodrilus axi, "in a clade we name Dinophiliformia that is sister to Errantia and Sedentaria" No linnaean rank is given for the clade but Errantia and Sedentaria are usually Annelida subclasses, whereas a '-formia' name is usually an order.